MENDELIAN RATIO AND CHROMOSOMES 503 
In regard to mosaics, Sutton says in part (’03, p.245) “If each 
cell contains paternal and maternal potentialities in regard to each 
character, and if dominance is not a common function of one 
of these, there is nothing to show why as a result of some disturb- 
ing factor one body of chromatin may not be called into activity 
in one group of cells and its homologue in another.’”’ This view 
is supported by blends which later segregate out pure characters 
as well as the work of Tennent (’10) reversing the dominance in 
Echinoderm hybrids by changing the concentration of the hy- 
droxylions in the sea-water in which they developed. 
A consideration of the limited number of chromosomes and the 
large number of characters in any animal or plant, will make it 
evident that each chromosome must control numerous allelo- 
morphs, or unit characters. It is to the individual dominance, 
either partial or complete of these unit characters, rather than 
to the dominance of the chromosome as a whole, that we may 
look for the explanation of Mendel’s laws. 
Since the rediscovery of Mendel’s laws, increased knowledge 
has been constantly bringing into line facts that at first seemed 
utterly incompatible with them. There is no cytological explana- 
tion of any other form of inheritance; the long association of syn-. 
aptic pairs during the growth period has suggested the possibility 
of some interaction between the chromosomes, but this associa- 
tion is between the chromosomes of the grandparents, directly. 
Let us suppose that these represent pure lines on both paternal 
and maternal sides, and that the character under consideration is 
a blended one. Now, the fertilized ovum resulting from a cross 
between these two pure lines at once develops an organism 
with the blended character without any long association of the 
chromosomes that produce it. In other words, if there were an 
interaction between chromosomes during the growth period, 
which would result in blended inheritance, it could not be mani- 
fested until the second hybrid generation. It seems to me 
probable that all inheritance is, in reality, Mendelian.’ 
2 All observational work was done at the University of Kansas. Some draw- 
ings have been completed and the paper revised at the University of Pennsylvania. 
